Fire Management

Prairie Fires and Grazing

Fire was a natural event on the Northern Tallgrass Prairie and
was started by lightning or Native American hunters who were driving game. In
western Minnesota, fire was the dominant force in shaping grasslands. This area
generally receives enough rain to support trees, but fire, bison grazing and
periodic drought helped to keep the forests from expanding westward.

As humans settled and the prairie was broken and fragmented,
fires could not carry across the expanses they once did. Whether it was a fire
or intense short term grazing by nomadic bison, grassland plants evolved a
dependence on frequent disturbance. Today, fire, haying, and grazing are used to
stimulate native grasses. The District has to rely on local farmers and ranchers
for assistance with haying and grazing. These activities can be detrimental if
they are not carefully planned. Fire can be an inexpensive and controlled way
for us to successfully manage a prairie tract.

Fires are conducted by highly trained staff using a variety of specialized
equipment such as fire engines, drip torches, all-terrain vehicles, and water
pumpers. Conditions like wind direction, wind speed, temperature, relative
humidity, safety, and smoke dispersal have to meet a designated set of criteria
called the "prescription." A plan must be written that sets those criteria and
provides guidelines for potential issues that could arise during a prescribed
fire. If those criteria are met, the fire can be conducted.

Large tracts are frequently divided into smaller burn units that
are more manageable as well as biologically beneficial. Leaving a portion of a
tract unburned provides a refuge for animals and insects that will return to the
burned area as it begins to grow again. A burn unit is typically burned once
every three to seven years. When establishing new grassland, it can be
beneficial to burn it both the third and fifth year after seeding. Grasslands
are burned primarily in spring and fall but may be burned in summer also. The
timing of the burn depends on the objective for that tract of land. Some of our
burn objectives include: stimulating grassland seeding or native prairie,
setting back the growth of invading trees, removing plant litter that has built
up over time, reducing fuel (layers of plant litter) around towns, rural homes
and barns, and stimulating grassland plant seed production.

Prairie plants evolved with fire and grow vigorously and produce
more seed following a fire. They grow more robust after a fire because the plant
litter has been removed from the soil surface, which results in higher soil
temperatures and increased nutrient availability. Prairie animals also evolved
with fire and usually escape unharmed. Burrowing animals seek shelter from fire
in their underground burrows. Birds can fly and animals can run away from on
coming fire. Some nests are destroyed by fire, but ground nesting birds like
waterfowl, prairie chickens, and songbirds have evolved with fire and predation.
When a nest is lost, these species will usually re-nest. Because predation is so
high on ground nesting birds, re-nesting is the only way these species have
successfully maintained their populations over time. Nesting cover and food
provided by the robust and diverse plant growth that follows a fire generally
benefits ground nesting birds for four to six years after the fire.